This invention relates to orthodontic appliances and, in particular, to an orthodontic appliance for controlling the movement of teeth in one or more directions.
Malocclusion, the misalignment of the maxillary (upper) and mandibular (lower) teeth when the jaw is closed, is a common problem usually occurring with the eruption of the permanent teeth. If left untreated, malocclusion can lead to headaches, disfigurement, deformation of the jaw, premature wearing of the teeth, and eventual tooth loss.
There are many appliances available to an orthodontist or correcting malocclusion. One type of appliance uses a mall screw jack attached to selected maxillary teeth. A problem with such an appliance is the limited motion available from the screw jack, i.e. motion is limited to a direction parallel to the length of the screw.
Although the human body is generally characterized as having bilateral symmetry, there are asymmetries in any given individual. In the mouth, the causes of malocclusion are rarely symmetrical and implicit in existing orthodontic appliances is an oral symmetry that often does not exist in fact. Because of asymmetries, the corrective movement of each tooth must be controlled by a combination of treatments with different appliances. If the appliances must be used consecutively, the treatment of a patient is prolonged.
Asymmetry is not the only reason appliances may have to be used consecutively. Class II malocclusion is the most common and usually occurs because the mandible (jaw one) is recessive, i.e. positioned further back than it ought to be, giving the appearance of protruding front teeth. The typical treatment is to expand the maxillary arch and advance the mandible. A problem with this technique is that opposing molars may become misaligned, unless the molars are distalized (moved further back in the mandible). In order to complete the treatment, two consecutive appliances are necessary: a first appliance to advance the mandible and expand the arch and a second appliance to distalize the molars. The second appliance is often the "headgear" seen on young adolescents
A problem with headgear, or with any removable appliance, is the need for compliance by the patient. Unless instructions are followed faithfully, treatment becomes an approximation of the orthodontist's program.
Another problem with headgear is that it operates on both sides of the mouth simultaneously. A difficult problem is known as a Class II subdivision. "Subdivision" refers to the fact that the teeth are not symmetrically positioned relative to a median line through the mouth. For example, the teeth on the right side of the mouth are in the correct biting position and the cuspid and/or eye tooth are out of position in the left side of the mouth. Expanding the maxillary arch and using headgear will distalize the molars on both sides of the mouth.
A particularly difficult Class II subdivision is when a tooth erupts in the palate rather than in the arch. It is difficult to move such a tooth into the arch. First the tooth has to be extruded or forced into the arch and then tipped into the correct position. For example, if a cuspid erupts in the palate and the root must be moved into the buccal plate, correction may take six months to a year just to complete this one process.
Tipping of teeth also occurs as a result of banding, wherein an anchor is bonded to each tooth and the anchors are interconnected with a wire. As the teeth move, they tip. The initial wire is then replaced with a rectangular wire and the teeth are torqued into position.
Expanding the maxillary arch opens the sutures or joints between the places of the skull, e.g. the midpalatine suture, the frontal nasal suture, and the zygomatic suture. These sutures do not open in the sense of forming a gap but grow together as the places are forced part. In patients with a cleft palate, there is no bony union. It is tissue and expanding the suture can tear the tissue. What is sometime desired is an appliance which can serve as a platform for holding the teeth in position during reconstruction.
Some older patients have patent sutures, i.e. sutures at are locked and cannot be activated. A surgeon either opens the suture with a hematome or scores the maxillary arch by cutting through the maxillary sinus in segmenting the arch. It is desirable to activate the suture while it segmented, move the segments into the desired position, and then fix the segments in place.
All of the procedures described above take time and can be combined in various ways, depending upon the needs of the patient, for a complete treatment that can take from eighteen to thirty months.
In view of the foregoing, it is therefore an object of the invention to provide an orthodontic appliance for moving teeth in more than one direction simultaneously.
Another object of the invention is to provide an orthodontic appliance for asymmetrical correction of malocclusion.
A further object of the invention is to provide an orthodontic appliance which can move teeth without tipping.
Another object of the invention is to provide an orthodontic appliance which can do simultaneous processes that were formerly done sequentially.
A further object of the invention is to provide an orthodontic appliance which can serve as a platform for positioning segments during reconstruction of the palate.